Minor packaging issue: no point in keeping 64-bit protoc.exe and the C# codegen plugin in the Grps.Tools NuGet packages. There is no 64-bit Windows in the world that would be incapable of running 32-bit executables (in fact, many programs are 32-bit only; Visual Studio and Firefox are just two examples).

NOTE (2018-12-07):
The issue is now invalid. There is a variant of Windows distribution packaging that supports 64-bit executables only: the nanoserver Docker image (docs) of Windows Server. From the above link, in case content gets moved:

Because Nano Server is optimized as a lightweight operating system for running “cloud-native” applications based on containers and micro-services or as an agile and cost-effective datacenter host with a dramatically smaller footprint, there are important differences in Nano Server[...]:

• Only 64-bit applications, tools, and agents are supported.

END NOTE

IDK about other platforms. It is possible to be missing the 32 bit libc.so on Linux, AFAIK, so a 32-bit binary would not run where a 64-bit would. But the Windows one definitely just takes up space.